Latency problems on a fairly recent PC

I have and old PC with the following CPU and onboard Graphics

- Intel Core2 Quad CPU Q6600 @2.4GHz
- NVIDIA Corporation C73 [GeForce 7100 / nForce 630i] (rev a2)

The motherboard is Gigabyte GA-73PVM-S2H ( www.gigabyte.com/Motherboard/GA-73PVM-S2H-rev-10#ov )


According to what I read I should be getting low Jitter but I get

Max Jitter (1ms thread)

423122 (ns)

Max Jitter (25μs thread)

21171 (ns)

Before trying an external PCI-e graphics card (I can't any laying around) to see if improves latency, what else should I try?

Isn't this jitter too large for this setup?

I installed Debian Wheezy as is. No configuration at all on the machine.




uname -a prompts:

Linux cnc1 3.4-9-rtai-686-pae #1 SMP PREEMPT Debian 3.4.55-4linuxcnc i686  GNU/Linux

That's horrible latency.

Might be worth trying latency-histogram to see if it is a single huge value every once in a while.

Possibly SMI?

Have you disabled everything not needed in BIOS?
Absolutely disable hyper threading and speed step and sleep modes and everything pertaining to power saving, including pci-e power saving, serial at a power saving etc.
Find an ATI or AMD graphic card, as you can not disable power saving for nvidia cards.

Thanks for the reply.

I will just do what you propose in the BIOS (I am running optimum defaults).

Also I found an Asus Radeon HD7770 1GB to test out.

Does this histogram screen-shot tells you anything? I am not sure what I am watching.

And moments later

takeda wrote: Thanks for the reply.

I will just do what you propose in the BIOS (I am running optimum defaults).

Also I found an Asus Radeon HD7770 1GB to test out.

Make sure you disable all power saving in the BIOS (including and speed switching or C states above C1)
"optimum defaults" are probably sub-optimum for real time

Also as others have mentioned, NVidia bad for real time

On seldom spices: Has anybody tried difference when replacing hdd by ssd?

Changing to a PCI express GPU (as mentioned above) makes no difference. Still the same levels of max jitter.

I don't see how this could be relative to SMI as it does not make a difference the time vs max jitter. It's 425 micro sec on 1millisecond thread right from starting up the latency-test executable.

Also the BIOS has no such settings. I will add some screenshots.